The amount, and speed, of weight loss in the first six months after bariatric surgery is mainly determined by genes, so one person's results are in no way predictive of anyone else's. There are gender-specific differences in weight loss that you'll also likely benefit from.
Genetic expression, however, is dependent upon environment, so we can all help our DNA along after surgery -- and for the rest of our lives -- by following key evidence-based bariatric rules such as no liquids 30 mins before or after meals, staying hydrated, practicing portion control, mindful eating, protein first veggies second, chewing food extremely well before swallowing, not slipping back into old eating behaviours and food habits, reading labels if you eat packaged foodstuffs, getting in at least 150 minutes of moderate intensity aerobic physical activity per week, getting enough sleep, and taking all of the required vitamin and mineral supplements.
Wishing you well with your surgery!